This technology is related to various chemical and mechanical industrial processes that need to collect, entrap, recover and separate solid particulates measuring five (5) microns or less from a dynamic gas system fine. Today, industry primarily depends on various types of wet scrubbers and filter and bag collectors to prevent fine particulates from escaping into the atmosphere. Recovery of materials collected in bag collectors is costly and may not be practical especially when processing food products that have limited shelf life. The handling and disposal of bags can also be difficult and costly. Wet scrubbers, while effective, are even more costly because of the additional liquid/solid extraction step and the additional cost of drying.
In a cyclone separator, a gas with particles therein, such as the smoke from a coal-fired power plant, enters a cylindrical or conical chamber tangentially and leaves axially. Because of the change in direction of the combined gas/particle mixture, the particles are flung to the outer wall, while the gasses whirl around to a central exit port. When a high percentage of fine particles are in the gas stream, the collection efficiency of a cyclone separator is poor. Cyclones have been electrostatically enhanced to improve performance. There are still disadvantages to known electrostatically enhanced cyclones.
U.S. Pat. Nos. 4,352,681 (Dietz), 4,588,423 (Gillingham et al.), and 5,591,253 (Altman et al.) disclose electrostatic dynamic separators that use internal corona charging methods to impart a charge on the particles to assist in the separation process. These cyclone separators effectively charge conductive and non-conductive particles because of the internal availability of both corona discharge electrodes and inductive electrodes. In many industrial processes that precede the cyclone in the gas stream flow, the particles are triboelectrically charged because of contact with dissimilar materials. If pre-charging is required, the particles pass through a corona field prior to entering the cyclone.
A disadvantage with using an internal corona discharge in the cyclone as described in the Dietz patent is that a corona discharge generates a corona wind that is difficult to keep symmetrical and uniform in a dust environment. In addition, the corona discharge adds an undesirable turbulence in situations where a streamlined flow is desired.
Altman et al. attempts to overcome some of the disadvantages of Dietz and Gillingham et al. by using slits to achieve a flow of a thin layer of material. The objectives are similar in that both devices try to achieve more effective methods for charging the particles of the entering gas stream.
Small cyclones come close to meeting the latest DOE "less than 2 micron" requirements and could be more cost effective then other systems if they were capable of remaining efficient as their size and through-put increases. A need exists for a cyclone that meets the latest DOE standards irrespective of size.